1. Technical Field
The present invention relates to an antenna array or assembly of arrays. More particularly, the present invention relates to modular, active phased antenna arrays.
2. Description of the Background Art
A phased array includes an array of radiating elements, or radiators, whose signals are controlled by a beamformer to produce an antenna beam pattern that may be steered, or scanned, in different directions. Phased array technology was originally developed for unidirectional, receive-only applications, such as radio astronomy, and then extended to bidirectional, transmit and receive applications, such as radar.
In a passive phased array, each radiator is coupled to a passive antenna module. For example, a passive electronically scanned array (PESA) is a bidirectional, passive phased array in which a radio frequency (RF) source provides a constant-phase, high-power transmit (Tx) signal to each passive antenna (or phase shift) module. In an active phased array, each radiator is coupled to an “active” antenna module. For example, an active electronically scanned array (AESA) is a bidirectional, active phased array in which an RF source provides a low-power Tx signal to each active, transmit/receive (T/R) module. One AESA application is the United States Navy's Cobra Judy program, which is a multi-story, data collection sensor mounted on the USNS Observation Island that is used, inter alia, to ensure compliance with various international treaties.
These radar systems can be very expensive, and one important cost component is replacement parts. Like the Navy's Cobra Judy program, AESAs have been adapted to a variety of military applications, and are, consequently, subject to hazardous environmental conditions. For example, a shipboard AESA may be subjected to severe weather as well as enemy fire, and if the AESA is damaged, the entire antenna is likely to stop functioning, which necessitates the replacement of the damaged component(s). Beyond the cost of replacing the entire component, a technician will oftentimes need to wait until the AESA can be dismantled in order for the damaged component to be replaced. Unfortunately, AESA repair typically occurs in-port, which may severely impact time-on-station. For certain applications, AESA data is most crucial when weather conditions are the harshest, and a system that can be repaired at sea, and at a reasonable cost, would greatly reduce this loss of time on-station.